Refund from Computicket

I bought tickets at checkers kiosk 19/07/18 for a show on the 29th September 2018 for R400 . When purchasing the ticket, the early bird tickets showed as sold out but later saw on the app that they were still available for R300. I went to checkers to enquirer about it and tickets were still available 20/07/18. I asked to cancel and the cashier called the Computicket but the consultant on the other end of the line was rude and wanted to charge 15% for a show that is Two months away. According to the system, they only charge if the show is 30 days or less. I didn’t get my full refund